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  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C231/00—Preparation of carboxylic acid amides
  • C07C231/02—Preparation of carboxylic acid amides from carboxylic acids or from esters, anhydrides, or halides thereof by reaction with ammonia or amines
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C303/00—Preparation of esters or amides of sulfuric acids; Preparation of sulfonic acids or of their esters, halides, anhydrides or amides
  • C07C303/02—Preparation of esters or amides of sulfuric acids; Preparation of sulfonic acids or of their esters, halides, anhydrides or amides of sulfonic acids or halides thereof
  • C07C303/22—Preparation of esters or amides of sulfuric acids; Preparation of sulfonic acids or of their esters, halides, anhydrides or amides of sulfonic acids or halides thereof from sulfonic acids, by reactions not involving the formation of sulfo or halosulfonyl groups; from sulfonic halides by reactions not involving the formation of halosulfonyl groups
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C303/00—Preparation of esters or amides of sulfuric acids; Preparation of sulfonic acids or of their esters, halides, anhydrides or amides
  • C07C303/26—Preparation of esters or amides of sulfuric acids; Preparation of sulfonic acids or of their esters, halides, anhydrides or amides of esters of sulfonic acids
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C51/00—Preparation of carboxylic acids or their salts, halides or anhydrides
  • C07C51/58—Preparation of carboxylic acid halides
  • C07C51/60—Preparation of carboxylic acid halides by conversion of carboxylic acids or their anhydrides or esters, lactones, salts into halides with the same carboxylic acid part

Definitions

• the present invention relates to a cost-effective two-step process for the manufacture of amino acid based surfactants using same surfactants as catalysts for synthesizing the intermediate of high quality and with quantitative yield. More particularly, the present invention relates to a process for the preparation of N- acyl amino acid surfactants by catalyzing the synthesis of fatty acid chloride by the same /V-acyl amino acid surfactants that are being manufactured.
• N- Acyl amino acid surfactants are widely used in personal care applications in addition to the other industrial applications. They fall in the category of anionic surfactants and are significantly milder than the rest of the anionic surfactants.
• anionic surfactants like sodium lauroyl sarcosinate, sodium myristoyl sarcosinate, sodium cocoyi glycinate, sodium cocoyi /V-methyl taurate are commercially used in face washes, body washes since they exhibit good cleansing power and are milder to skin and hair compared to other anionic surfactants.
• Alkanoyl sarcosinates find applications in mouth washes and in dentifrices, in general, due to their bacteriostatic activity.
• N- acylated amino acids are commercially used such as in petroleum products, as lubricants, in metal processing and ore floatation.
• surfactants J.D. Spivack, Chapter 16, in 'Anionic surfactants, Vol 7, Surfactant Science Series, Edited by W. M. Linfield.
• they are manufactured from a two-step synthesis that involves fatty acid and various amino acids such as glycine, sarcosine, /V-methyl taurine, alanine, aspartic acid, glutamic acid, glutamine and arginine. These are some of the most commonly used amino acids that are used to manufacture /V-acyl amino acid surfactants.
• amino acids chiral or racemic, natural or synthetic can be used in the manufacture of /V-acyl amino acid surfactants.
• amino acids used in the surfactant manufacture do not have to be a- amino acids.
• the acid group in these amino acids can be any other acidic group other than the carboxylic group.
• Amino sulphonic acids e.g. /V-methyl taurine
• the precursors of /V-acyl amino acid surfactants, the fatty acid chlorides, industrially, are manufactured by reacting fatty acids and a halogenating agent, either phosgene or thionyl chloride as depicted in schemes 2 and 3.
• the chlorination is usually catalyzed by N, N- dimethyl formamide (DMF).
• DMF or similar substituted formamides form a complex (Vilsmeier complex) with COCI 2 or SOCI 2 which is the actual catalytic species (US 5,430,186; US 5,623,082; US 5,200,560; US 5,278,328 & US 5,166,427) in chlorination of acids.
• Distillation is another way to isolate the product but not all acid chlorides are amenable to distillation.
• the catalyst complex (Vilsmeier complex) exists in ionic form and hence is not easy to get rid of the same by distillation/fractionation of acid chloride. The complex keeps decomposing while distilling. Secondly, the losses of distillation/ fractionation (fractions with formamide catalyst and residue left after the distillation) are unavoidable.
• DMF formamides or any other organic molecules similar to DMF.
• DMF is listed in hazardous substances and is reported have chronic toxic effect and health hazard rating of 2.
• no toxicity data are available for the other formamides, the analogues of DMF that are capable of being catalysts but are expected to exhibit similar or higher toxicity.
• the analogs of DMF do suffer from the same difficulty of isolating fatty acid chloride (product) from the reaction mass when used as catalysts since they do form Vilsmeier complexes with halogenating agents.
• the fatty acid chlorides made by halogenating fatty acids either with phosgene or thionyl chloride using formamides, acetamides, or any other analogues as catalysts need additional steps of purifications such as distillation, phase separation or crystallization etc. These additional steps result in significant loss of yield, higher energy consumption and longer batch cycle time resulting into lower productivity. Since the making of the key intermediates, the fatty acid chlorides, by the current processes of the existing art, is cumbersome and inefficient, it impacts the quality and the cost of all downstream products such as the /V-acyl amino acid surfactants with world consumption of is estimated to be 250,000 metric tonnes.
• the present invention relates to the manufacture of amino acid based surfactants using same surfactants as catalysts for synthesizing the intermediate of high quality and with quantitative yield.
• the overall process is 'green' (significantly reduced batch time, low energy consumption, without any wastage and effluent generation (no residue after distillation/fractionation), and extremely cost-effective (low energy consumption), efficient (faster rate of catalysis).
• this process described in the present application avoids use of toxic catalysts and is applicable to entire class of /V-acyl amino acid surfactant family.
• the present invention relates to a process of producing /V-acyl amino acid based surfactants of Formula I, Formula I
• R is selected from C6 to C22 alkyl group
• Ri is selected from H, C1 to C4 alkyl
• R 2 is selected from all groups on a carbon of natural amino acids
• R 3 is selected from COOX, CH 2 -SO 3 X
• X is selected from Li + , Na + or K + ;
• R C6 to C22 alkyl group
• Ri H
• R 2 all groups on a carbon of natural amino acids
• n 0 to 4
• X C, SO and
• step (B) reacting fatty acid chloride of step (A) with an amino acid in the presence of a base under typical aqueous Schotten Baumann conditions such that said process does not employ a step of purification .
• the present invention relates to a cost-effective process for the manufacture of amino acid based surfactants using same surfactants as catalysts for synthesizing the intermediate of high quality and with quantitative yield.
• the method of this invention teaches the manufacture of /V-acyl amino acid surfactants of Formula I Formula I
• R represents alkyl chain with carbon atoms ranging from 6 to 22
• Ri represents H, or small alkyl chains ranging from C1 to C4
• R 2 represents all groups on a carbon of natural amino acids
• the process of the present application involves two steps.
• the first step is the manufacture of fatty acid chloride and in the second step the fatty acid chloride manufactured in the first step is reacted with an amino acid in aqueous or mixed water- solvent medium in the presence of base to obtain the A/-acyl amino acid surfactants.
• the alkyl chain represented by R can be even numbered or odd numbered, linear or branched chains. It can be a single chain or a mix of several alkyl chains ranging from C 6 to C 22.
• the alkyl chain can be completely saturated or it can be unsaturated with one or more double bonds. Since these alkyl chain are derived from fatty acids that occur in nature, mostly, in the form of animal fats or vegetable oil. Unsaturated alkyl chains can be derived from oleic acid, recinoleic acid, linolic acid, linolenic acid, elaeosteric acid, eicosenoic acid, euricic acid, docosodienoic acid and undecylenic acid.
• the saturated fatty acids are usually derived from palm/palm kernel oil or coconut oil and are all even numbered ranging from octanoic acid (C8) to stearic acid (C18).
• Fatty acids with higher number of carbons (C18 to C22) are derived from mustard oil, tung oil and rapeseed oil.
• the saturated/unsaturated fatty acids are converted to the corresponding acid chlorides by either treating them with thionyl chloride or phosgene. Both reactants are reacted with each other in stoichiometric equivalent quantity or up to 3% excess of chlorinating agent (mole ratio, fatty acid : chlorinating agent::1 :1.03).
• halogenations of fatty acids with either phosgene or thionyl chloride are done at 20 to 45 ° C under nitrogen blanket with a scrubbing system for absorption of by-products HCI and S0 2.
• a scrubbing system for absorption of by-products HCI and S0 2.
• S0 2 and HCI are separated and are conveniently used whereby S0 2 is converted back to SOCI 2.
• the types of amino acids that are used in the synthesis of compounds of Formula I are naturally occurring a-amino acids (Glycine, Alanine, Valine, Leucine, Isoleucine, Methionine, Proline, Cystein, Phenyl alanine, Tyrosine, Tryptophan, Arginine, Lysine, Histidine, Aspartic acid, Glutamic acid, Serine, Threonine, Aspergine, Glutamine), unnatural amino acids (opposite 'D' stereochemistry), mixtures of stereoisomers, unnatural amino acids (amino propionic acid, /V-methyl taurine, Sarcosine).
• the amino acids required for the synthesis of compounds of Formula I need to have one primary or secondary amino group at one end and an acid group, either carboxylic or sulphonic at the other end.
• fatty acid chloride is added to a cooled (10 to 15 ° C) and stirred aqueous solution of amino acid in its salt form with alkali metals.
• the cations of salt form of the amino acids are alkali metal ions like potassium, sodium or lithium.
• the ratio of fatty acid chloride to amino acid varies from 1 :1 to 1 :1 .03.
• one equivalence of base (in solution form) and one equivalence of fatty acid chloride are added simultaneously maintaining the stoichiometric ratio and the pH of the reaction mass between 10 to 1 1 , preferably between 10.3 to 10.6.
• the Schotten-Baumann reaction is a rapid reaction and results in very clean product with stoichiometric generation of byproduct, the salt, alkali metal chloride, depending on the base employed. Small extent of hydrolysis of fatty acid chloride does result in generation of corresponding alkali metal salts of fatty acids.
• the /V-acyl products that are obtained are practically colorless and odorless. The products obtained are free of any contamination due to the residual catalyst since the catalyst used is the same surfactant that is being manufactured.
• the present application teaches the use of /V-acyl amino acid catalysts for the manufacture of fatty acid chloride that would give the same surfactant after performing the second step of Schotten Baumann reaction.
• the fatty acid chloride step employs 0.05 to 2 mole % of /V-acyl amino acid surfactants as catalysts.
• synthesis of sodium cocoyl glycinate is accomplished using cocoyl chloride that was made from reaction of coco fatty acid and thionyl chloride catalyzed by sodium cocoyl glycinate itself.
• Example No. 6 describes, synthesis of sodium lauroyl glycinate from lauroyl chloride and glycine in the presence of base. The lauroyi chloride for this conversion was synthesized from lauric acid and thionyl chloride under the catalytic influence of sodium lauroyi glycinate.
• Proton magnetic resonance spectrum of the same molecule in deuteriated chloroform showed the signal for methylene protons of glycine moiety at ⁇ 2.46.
• the lauroyi chloride obtained was practically colorless with very good conversion (Table 1 in Experiment 1 ).
• This lauroyi chloride was then used without any purification and was reacted with stoichiometric quantity of glycine in water at 10 to 15 ° C in the presence of equivalent quantity of base (Experiment 1 ).
• the competing nucleophile water (alkaline pH) can hydrolyze the anhydride to yield sodium lauroyi glycinate and sodium laurate.
• the final product that is aqueous solution of sodium lauroyi glycinate with 30 % solids content will have 0.0002 mole % of sod laurate generated by hydrolysis of the anhydride catalyst is.
• R 2 H, Ci to C 4
• sodium lauroyi glycinate, the /V-acyl amino acid surfactant, prepared from the above lauroyi chloride obtained by using either sodium lauroyi glycinate (Formula III, R C1 1 , R 2 H) as a catalyst or /V-lauroyl glycenic lauric anhydride (Formula III, R
• any /V-acyl amino acid surfactant essentially can catalyze chlorination of any fatty acid or mixture of fatty acids to yield corresponding fatty acid chlorides at 0.02 to 2.0 mole % concentration level.
• Example 8 shows a facile synthesis of sodium cocoyl glycinate wherein the synthesis of cocoyl chloride is accomplished by catalyzing reaction between coco fatty acid and thionyl chloride by sodium /V-lauroyl, /V-mehtyl taurate.
• fatty acid chlorides thus produced are not only suitable for a batch process of Schotten Baumann reaction but also for a continuous process for manufacturing /V-acyl amino acid surfactants by reacting fatty acid chlorides, amino acid salts and the bases.
• the process described is very cost-effective since it avoids purification steps that result in significant reduction in energy consumption.
• the process of the present invention also avoids laborious steps of purifications and loss of product that entails the purification steps.
• the process avoids all the toxic catalysts used in the prior art.
• the two-step process is absolutely 'green' since it does not generate any effluent (no waste disposal), consumes less power, involves fewer unit operations, affords quantitative yields and above all, uses a biodegradable, eco-friendly catalyst.
• the present patent application discloses a self-catalyzed /V-acyl amino acid surfactant synthesis.
• the catalyst for the intermediate acid chloride is the same surfactant that is being manufactured and hence the intermediate fatty acid chloride does not have to be purified by additional steps (distillation/crystallization) that often lead to the suDstantiai loss of yield and increased batch cycle time and increased energy consumption.
• the /V-acyl surfactant catalysts work equally well with both industrial halogenating agents. These catalyst work very well with phosgene and thionyl chloride while creating fatty acid chloride
• the by-product of phosgenation is C0 2 whereas with thionyl chloride the by-product is S0 2 that can be converted into surfuryl chloride and subsequently thionyl chloride by a well established 'closed loop' chemistry(US 5,489,400).
• Fatty acids were procured from Natural Oleo-chemicals, Malaysia whereas thionyl chloride from Transpek Industries, Vadodara, India. Phosgene trimer, glycine and sodium /V-methyl taurate were procured from Aldrich. The color value is used as an indication of the purity of the acid chloride product. The color value of intermediates and A/-acyl amino acid surfactants was determined on APHA scale by Lovibond PFX995/950. Fatty acid chlorides were analyzed as per the analytical method described in "Quantitative Organic Analysis Via Functional Groups", Editors :Sidney Siggia and J. Gordon Hanna, 4 th Edition (Pg. 223 - 230), John Wiley & Sons (1979).
• Coco fatty acid that was used to make the catalyst I (/V-cocoyl glycenic cocoyic anhydride
• Ci8 (Stearic acid)-2.0%
• Preparation of sodium cocoyi glycinate by a two step procedure that comprises of a) Preparation of cocoyi chloride from coco fatty acid and thionyl chloride in the presence of catalytic amount of a sodium cocoyi glycinate and b) Preparation of sodium cocoyi glycinate from cocoyi chloride of step (a) and glycine in aqueous medium
• Cio Capric acid
• Ci2 (Laurie acid)-61 .37 %
• Ci 8 (Stearic acid)-2.0%
• Preparation of sodium lauroyi glycinate by a two step procedure that comprises of a) Preparation of lauroyi chloride from lauric acid and thionyl chloride in the presence of catalytic amount of a sodium lauroyi glycinate and b) Preparation of sodium lauroyi glycinate from lauroyi chloride of step (a) and glycine in aqueous medium
• Preparation of sodium /V-lauroyl, /V-methyl taurate by a two step procedure that comprises of a) Preparation of lauroyi chloride from lauric acid and thionyl chloride in the presence of sodium /V-lauroyl, /V-methyl taurate and b) Schotten-Baumann reaction of lauroyi chloride of step (a) with sodium /V-methyl taurate in the presence of a base.
• Preparation of sodium cocoyl glycinate by a two step procedure that comprises of a) Preparation of cocoyl chloride from coco fatty acid and thionyl chloride in the presence of catalytic amount of a sodium /V-cocoyl, A/-methyl taurate and b) Preparation of sodium cocoyl glycinate from cocoyl chloride of step (a) and glycine in aqueous medium
• Coco fatty acid that was used to make cocoyl chloride had the following composition :
• Ci6 (Palmitic acid)-4.7 %
• Ci 8 (Stearic acid)-2.0%
• coco fatty acid 200 g, 1 .0 gmol
• sodium /V-cocoyl, /V-methyl taurate 0.6 g, 0.0017 gmol
• thionyl chloride 123 g, 1 .029 gmol
• the hydrochloric acid and sulfur dioxide generated during the process was continuously scrubbed in a gas scrubber containing caustic lye.
• the reaction mixture was stirred for additional 4 hours at the reaction temperature. The progress of reaction was monitored by measuring alkanoyl chloride formation.

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